Toner transporting method and mechanism employing a belt conveyor

ABSTRACT

An electrophotographic printer has a toner recycling  transporting mechanism with a belt conveyor that transports toner from a toner collection chamber, in which toner removed from the photosensitive drum of the printer is collected, to a toner delivery chamber, from which toner is returned to the developing unit of the printer . The belt conveyor is disposed in a channel that loops around the ends of roller shafts in the printer, and does not increase the width of the printer. The toner recycling  transporting mechanism is easily assembled, and can be driven without motion irregularities.

BACKGROUND OF THE INVENTION

The present invention relates to a method and a mechanism for recyclingtransporting toner in an electrophotographic printer.

An electrophotographic printer forms a lateral electrostatic image on aphotosensitive drum, develops the image by application of toner, thentransfers the toner from the drum to a printing medium such as a sheetof paper. In many electrophotographic printers, the photosensitive drumand developing unit are part of a replaceable cartridge that alsoincludes a cleaning unit for cleaning the photosensitive drum byremoving toner that fails to be transferred to the printing medium.

Many electrophotographic printers have a recycling mechanism thatreturns toner form the cleaning unit to the developing unit, so thattoner recovered by the cleaning unit can be reused. Such recycling oftoner has several advantages: more pages can be printed before the tonersupply has to be replenished; no tank is needed to store toner removedby the cleaning unit; and the toner removed by the cleaning unit doesnot have to be disposed of.

The toner recycling mechanism is part of the replaceable cartridge. Aconventional toner recycling mechanism comprises three helical screwconveyors. The first screw conveyor conveys toner to one end of thecleaning unit. The second screw conveyor conveys toner from this end ofthe cleaning unit to the corresponding end of the developing unit. Thethird screw conveyor conveys toner into the developing unit.

The replaceable cartridge also includes various rollers, such as adeveloping roller for applying toner to the photosensitive drum and asupply roller for supplying toner to the developing roller. The firstand third screw conveyors of the toner recycling mechanism are orientedparallel to these rollers, but the second screw conveyor is oriented ata right angle to the rollers. To avoid interference with the rollers,the second screw conveyor must be disposed at one side of the cartridge,beyond the ends of the roller shafts. The cartridge must accordingly bewidened to accommodate the second screw conveyor, but this undesirablyincrease the dimensions of the printer.

Another disadvantage of the conventional toner recycling mechanism isthat the second screw conveyor must be driven by a gear train includinga worm gear. This type of gear train produces a thrust force that placesan extra load on the driving motor, leading to uneven motion andirregular printing. The existence of the worm gear train also makes thereplaceable cartridge more difficult to assemble.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide a tonerrecycling transporting method and mechanism that do not increase thedimensions of an electrophotographic printer.

Another object of the invention is to provide a toner recyclingtransporting method and mechanism that do not cause printingirregularities.

Another object is to provide a toner recycling transporting mechanismthat is easy to assemble.

The invented toner recycling transporting method uses a belt conveyor totransport toner from a toner collection chamber, in which toner removedfrom the photosensitive drum of an electrophotographic printer iscollected, to a toner delivery chamber, from which the toner is returnedto the developing unit of the printer .

The invented toner recycling transporting mechanism comprises a sideframe supporting one end of the shaft of a roller in the developing unitof the printer. The side frame has a channel forming a loop around theend of the shaft. A pick-up station is disposed at one end of the loop,and a discharging station at another end of the loop.

A cleaning unit removes toner from the photosensitive drum. The tonerremoved by the cleaning unit is held in a toner collection chamber thatopens into the channel at the pick-up station. A conveyor in the tonercollection chamber carries the toner to the pick-up station.

A belt conveyor disposed in the channel carries the toner from thepick-up station to the discharging station. At the discharging station,the toner is discharged into a toner delivery chamber, from whichanother conveyor returns the toner to the developing unit .

The belt conveyor preferably has ribs, pockets, cut-out holes, or teethfor carrying the toner. The belt conveyor may also have a longitudinalrib that fits into a groove in the channel, to prevent the belt conveyorfrom being installed in the wrong orientation. The belt conveyor maybedriven by a pulley disposed inside the loop of the channel, by a toothedwheel disposed outside the loop, or by a toothed end of the conveyor inthe toner delivery chamber. Torque may be transmitted to the beltconveyor by an idle gear turning on a stationary shaft, in which case agroove is preferably provided on the outer surface of the stationaryshaft, or the inner surface of the idle gear, to permit the escape oftoner or other foreign matter that becomes caught between the idle gearand stationary shaft. Vibration may be imparted to the belt conveyor byan interfering member to promote the release of toner at the dischargingstation.

The channel that houses the belt conveyor is disposed inboard of the endof the shaft of the roller in the developing unit, so the invented tonerrecycling transporting mechanism does not increase the dimensions of theprinter.

No worm gear is required to drive the belt conveyor, so printingirregularities due to the thrust produced by a worm gear are avoided.

The invented toner recycling transporting mechanism is easy to assemblebecause it has relatively few parts.

BRIEF DESCRIPTION OF THE DRAWINGS

In the attached drawings:

FIG. 1 shows a sectional view of an electrophotographic printer;

FIG. 2 shows a side view of a conventional toner recyclingtransportingmechanism;

FIG. 3 shows a plan view of the conventional toner recyclingtransportingmechanism;

FIG. 4 shows a side view of a toner recyclingtransporting mechanismaccording to a first embodiment of the invention;

FIG. 5 shows a perspective view of the toner recyclingtransportingmechanism in FIG. 4;

FIG. 6 is a partly cutaway perspective view showing the conveyor in thetoner collection chamber in FIG. 4;

FIG. 7 is a perspective view showing one possible configuration of thebelt conveyor in the first embodiment;

FIG. 8 is a perspective view showing another possible configuration ofthe belt conveyor in the first embodiment;

FIG. 9 is a perspective view showing another possible configuration ofthe belt conveyor in the first embodiment;

FIG. 10A, FIG. 10B, and FIG. 10C are side views of the first embodiment,illustrating the transport of toner by the belt conveyor;

FIG. 11 shows a side view of a toner recyclingtransporting mechanismaccording to a second embodiment of the invention;

FIG. 12 is a perspective view illustrating the gear train by which thetoner recyclingtransporting mechanism is driven in the secondembodiment;

FIG. 13 is a perspective view of the belt conveyor in the secondembodiment;

FIG. 14 is a side view illustrating the efficient vertical transport oftoner by the belt conveyor in the second embodiment;

FIG. 15 is a side view illustrating less efficient vertical transport oftoner by a belt conveyor with symmetrical teeth;

FIG. 16 is a schematic view comparing the scooping action of the beltconveyor in the second embodiment with the scooping action of a beltconveyor having symmetrical teeth;

FIG. 17 shows a side view of a toner recyclingtransporting mechanismaccording to a third embodiment of the invention;

FIG. 18 shows a perspective view of the belt conveyor in the thirdembodiment;

FIG. 19 is a sectional view through line X—X in FIG. 17, illustratingcorrect installation of the belt conveyor in the third embodiment;

FIG. 20 is a similar sectional view illustrating incorrect installationof the belt conveyor in the third embodiment;

FIG. 21 is a perspective view showing the side frame in a tonerrecyclingtransporting mechanism according to a fourth embodiment of theinvention;

FIG. 22 is an exploded perspective view of the idle gear and itsstationary shaft in the fourth embodiment;

FIG. 23 is a perspective view of the stationary shaft of the idle gearin a toner recyclingtransporting mechanism according to a fifthembodiment of the invention;

FIG. 24 is a perspective view of the idle gear in a tonerrecyclingtransporting mechanism according to a sixth embodiment of theinvention;

FIG. 25 is a side view showing a toner recyclingtransporting mechanismaccording to a seventh embodiment of the invention;

FIG. 26 is a side view showing a toner recyclingtransporting mechanismaccording to an eighth embodiment of the invention;

FIG. 27 is a perspective view of the toothed screw conveyor in theeighth embodiment;

FIG. 28 is a side view showing a toner recyclingtransporting mechanismaccording to a ninth embodiment of the invention; and

FIG. 29 is a side view showing a toner recyclingtransporting mechanismaccording to a tenth embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention will be described to reference to theattached illustrative drawings. As an illustration of the type ofprinter in which the invention can be employed, and of the type of tonerrecycling transporting mechanism that the invention replaces, a briefdescription of an electrophotographic printer with a conventional tonerrecycling transporting mechanism will be given first.

FIG. 1 shows the main parts of this printer. A paper cassette 2 holdssheets of paper 4, which are fed by hopping roller 6 and a pair oftransport rollers 8 on a paper path because a replaceable cartridge,referred to below as the printing process cartridge 10, and a transferunit 12. An optical printing head 14 creates an image that is developedin the printing process cartridge 10 and transferred by the transferunit 12 to a sheet of paper 4. The transferred image is fused onto thepaper by a fusing unit 16. A pair of delivery rollers 18 feeds theresulting printed pages to a face-down delivery tray 20 or a face-updelivery tray 22.

The printing process cartridge 10 comprises a photosensitive drum 24, acharging unit 26 that charges the photosensitive drum 24 to a uniformpotential preparatory to image formation, a developing unit 28 thatdevelops the image by applying toner, a toner cartridge 30 from whichthe toner is supplied, and a cleaning unit 32 that removes remainingtoner from the photosensitive drum 24 after transfer of the image to thepaper 4. The developing unit 28 comprises a developing roller 34 thatapplies toner to the surface of the photosensitive drum 24, and a supplyroller 36 that supplies toner to the developing roller 34.

FIG. 2 is an enlarged view of the printing process cartridge 10 as seenfrom the opposite side, showing the cleaning blade 38 of the cleaningunit 32, and the three screw conveyors 40, 42, and 44 of theconventional toner recyclingtransporting mechanism. The first screwconveyor 40 brings toner from the cleaning unit 32 to the base of thesecond screw conveyor 42, which carries the toner upward through aninclined passage 46 to the third screw conveyor 44, as indicated by thearrow. The second screw conveyor is driven by a gear train comprisinggears 48, 50, and 52.

FIG. 3 shows how the three screw conveyors 40, 42, and 44 are disposedin relation to the photosensitive drum 24, developing roller 34, andsupply roller 36, illustrating the fact that the printing processcartridge 10 must be widened to accommodate the second screw conveyor42. FIG. 3 also shows two additional gears 54 and 56 by which the firstscrew conveyor 40 is driven. The rotation of the photosensitive drum 24is transmitted by gears 54 and 56 to the first screw conveyor 40, thenby gear 48, 50, and 52 to the second screw conveyor 42. Gear 50 is aworm gear.

The rotation of the photosensitive drum 24 is also transmitted by gears(not shown) to the rollers 34 and 36 and the third screw conveyor 44.The photosensitive drum 24 is driven by a motor (not visible).

FIG. 4 shows a side view of a printing process cartridge 58 having atoner recyclingtransporting mechanism according to a first embodiment ofthe invention. The photosensitive drum 24 and the developing unit 28with its developing roller 34 and supply roller 36 are similar to thecorresponding elements in FIG. 1. Whereas FIG. 1 showed a charging unit26, FIG. 4 shows a charging roller 60, which makes contact with thesurface of the photosensitive drum 24 to apply a uniform electrostaticcharge. The printing process cartridge 58 also has a toner cartridge(not visible) similar to the one in FIG. 1.

The cleaning unit 62 in FIG. 4 has a cleaning blade 64 that scrapestoner from the surface of the photosensitive drum 24, allowing the tonerto fall into a toner collection chamber 66. A screw conveyor 68 bringsthe collected toner to one end of the toner collection chamber 66.

The side frame or toner recycling transporting portion 70 on theillustrated side of the printing process cartridge 58 has a channel 72that loops around the ends of the shafts of the photosensitive drum 24and the rollers 34 and 36 in the developing unit 28. The channel 72 isoccupied by a belt conveyor 74. A pulley 76 at one end of the channel72, disposed inside the loop of the channel 72, turns in the decision ofarrow A, moving the belt conveyor 74 in the direction of arrow B. At theother end, the channel 72 opens into the toner collection chamber 66 ofthe cleaning unit 62. The pick-up station 78 of the belt conveyor 74 isdisposed in the region where the channel 72 meets the toner collectionchamber 66 i.e., a first portion; the discharge station 80 of the beltconveyor 74 is disposed beneath the pulley 76 i.e., second portion. Thebelt conveyor 74 discharges into a toner delivery chamber 82, from whicha screw conveyor 84 carries toner to the developing unit 28.

FIG. 5 is a perspective view of the side frame or tonerrecyclingtransporting portion 70, showing that the ends of the shafts ofthe photosensitive drum 24, developing roller 34, supply roller 36, andcharging roller 60 extend outboard from the surface of the side frame ortoner recyclingtransporting portion 70, while the channel 72 extendsinboard from this surface. The channel 72 and belt conveyor 74accordingly do not increase the width of the printing process cartridge58. Nor is the width increased by the screw conveyors 68 and 84 andpulley 74, since the ends of their shafts extend less far outboard thando the ends of the shafts of the photosensitive drum 24, developingroller 34, supply roller 36, and charging roller 60.

FIG. 6 is a partially cutaway perspective view showing the screwconveyor 68 in the toner collection chamber 66. The side frame or tonerrecyclingtransporting portion 70 has a side cover that prevents tonerfrom escaping from the channel 72. This cover is also partially cut awayin FIG. 6, to show the pick-up station 78 where toner brought by thescrew conveyor 68 is transferred to the belt conveyor 74. To facilitatetransport of the toner, the belt conveyor 74 may have raised lateralribs 86 as shown in FIG. 7, or depressed pockets 88 as shown in FIG. 8.Alternatively, the belt conveyor 74 maybe a mesh belt with cut-out holes89 as shown in FIG. 9.

The invented toner recycling transporting mechanism operates as follows.The motor (not shown) that drives the photosensitive drum 24 also drivesthe pulley 76 and the screw conveyors 68 and 84. As the photosensitivedrum 24 turns past the cleaning blade 64, remaining toner is removed anddrops into the toner collection chamber 66. Screw conveyor 68 bringsthis toner to the pick-up station 78 at the lower end of the channel 72,as shown in FIG. 10A. The belt conveyor 74 carries the toner upwardtoward the pulley 76 as shown in FIG. 10B. At the discharge station 80,the toner carried by the belt conveyor 74 drops into the toner deliverychamber 82 as shown in FIG. 10C, and is fed by screw conveyor 84 to amore central part of the toner delivery chamber 82. From there, thetoner falls back into the developing unit 28, to be picked up by thesupply roller 36 and supplied again to the developing roller 34.

As pointed out above, the invented toner recycling transportingmechanism does not require the width of the printing process cartridge58 to be increased. The toner recycling transporting mechanism in thefirst embodiment is also easier to assemble than the conventional tonerrecycling transporting mechanism, because the belt conveyor 74 is drivenby a single pulley 76 instead of a worm gear train. The problem ofthrust that was present in the worm gear train is also eliminated, soprinting is more regular.

Next, a second embodiment will be described.

Referring to FIG. 11, the belt conveyor 74 in the second embodiment hasteeth 90 that project at an angle in the direction of motion (arrow B)of the belt conveyor 34. These teeth 90 engage the teeth of a beltdriving gear 92 which turns in the direction of arrow D and drives thebelt conveyor 74 around the channel 72. By pushing against the teeth 90of the belt conveyor 74, the belt driving gear 92 pulls the beltconveyor 74 downward in the drawing. The natural stiffness of the beltconveyor 74 also transmits the pushing force of the belt driving gear 92forward, so that the belt conveyor 74 is both pushed and pulled aroundthe channel 72.

The belt driving gear 92 also drives an idle gear 94, which drives agear 96 that turns the screw conveyor 84. The pulley 98 at the top ofthe channel 72 turns freely. The purpose of the pulley 98 in the secondembodiment is not to drive the belt conveyor 74, but to enable the beltconveyor 74 to negotiate the sharp turn at the top of the channel 72without friction.

FIG. 12 shows how the belt driving gear 92 is driven. The photosensitivedrum 24 is turned by a motor (not visible) as in the first embodiment. Agear 100 at one end of the shaft of the photosensitive drum 24, oppositefrom the end at which the toner recyclingtransporting mechanism isdisposed, engages a similar gear 102 at the end of the shaft of thedeveloping roller 34, so that the rotation of the photosensitive drum 24also turns the developing roller 34. The driving torque is transmittedthrough the shaft of the developing roller 34 to another gear 104. Gear104 drives an idle gear 106, which drive a gear 108 attached to theshaft of the supply roller 36. The photosensitive drum 24, developingroller 34, and supply roller 36 turn in the directions indicated byarrows E, F, and G.

The gear 108 attached to the shaft of the supply roller 36 also drives agear 110 attached to the shaft 112 of the belt driving gear 92 in thetoner recycling transporting mechanism. An idle gear 113 is providedbetween the gears 108 and 110, and the rotation of gear 108 istransmitted to gear 110 through idle gear 113, so that gear 110 turns inthe direction of arrow H. The belt driving gear 92 is thereby driven inthe direction of arrow D.

FIG. 13 is an enlarged view of the belt conveyor 74, showing the shapeof the teeth 90. The outer face 114 of the teeth preferably has a convexinvolute shape against which the teeth of the belt driving gear 92 canpress without friction. The inner face 116 has a concave involute shape,generally following the contour of the outer face 114.

Referring to FIG. 14, the shape of the teeth 90 of the belt conveyor 74,angled in the forward direction, enables toner to be efficientlytransported vertically upward. If the teeth of the belt conveyor 74 wereto have a symmetrical shape, vertical transport would be less efficient;toner would fall back, as illustrated in FIG. 15.

Referring to FIG. 16, the shape of the inner face 116 of the teeth 90 isalso suitable for scooping up toner in the toner collection chamber 66.As the belt conveyor 74 turns within the channel 72, scooping actionbegins when the inner end of a booth 90 is lower than the outer end. Thesloping inner face 116 of the teeth 90 permits scooping to being earlierthan would be possible with a symmetrically shaped tooth 118.

Referring again to FIGS. 11 and 13, the sloping outer surface 114 of theteeth 90 is also an advantage at the discharging station 80. Thissurface 114 slopes downward at the discharge station 80, allowing tonerto fall freely into the toner delivery chamber 82.

By enabling the belt conveyor 74 to transport and discharge tonerefficiently, without friction between the belt conveyor 74 and beltdriving gear 92, the second embodiment reduces the torque load on themotor, contributing to quieter operation of the printer, more uniformdriving of the photosensitive drum 24, and thus more uniform printedoutput.

The belt driving gear 92 need not be a gear with involute teeth; asprocket wheel of the type used to drive an automotive timing belt canbe used, or any other type of toothed wheel can be used, with suitablemodification to the shape of the teeth 90 of the belt conveyor 74.

Next, a third embodiment will be described.

Referring to FIG. 17, the channel 72 in the third embodiment has aninterior groove 120. The groove 120 is disposed in the floor of thechannel 72, and extends around the entire length of the channel 72,adjacent the inner wall of the channel 72.

Referring to FIG. 18, the belt conveyor 74 in the third embodiment issimilar to the belt conveyor 74 in the second embodiment, with teeth 90angled toward the intended direction of motion of the belt conveyor 74,but has an additional longitudinal rib 122 on one side. The longitudinalrib 122 extends for the entire length of the belt conveyor 74. Thelongitudinal rib 122 may be thinner than the body 124 of the beltconveyor 74, as shown in FIG. 18. Alternatively, the longitudinal rib122 may have the same thickness as the body 124 of the belt conveyor 74.

Referring to the sectional view in FIG. 19, when the belt conveyor 74 iscorrectly oriented in the channel 72, the longitudinal rib 122 fits intothe groove 120. The side frame or toner recycling transporting portion70 has a side cover 126 that fits snugly against the side frame or tonerrecycling transporting portion 70 when the belt conveyor 74 is installedin the correct orientation.

Referring to FIG. 20, if the belt conveyor 74 is installed in the wrongorientation, the longitudinal rib 122 projects above the surface of theside frame or toner recycling transporting portion 70, so that a gap Cis left between the side cover 126 and the side frame or toner recyclingtransporting portion 70. When the printing process cartridge 58 isassembled, if the belt conveyor 74 is mistakenly installed in the wrongorientation, the gap C makes the mistake obvious. The side cover 126cannot be attached to the side frame or toner recycling transportingportion 70 until the mistake is corrected. Assembly errors are thusavoided. The third embodiment assures that when the printing processcartridge 58 is assembled, the teeth 90 of the belt conveyor 74 arecorrectly oriented for scooping and transporting toner, and are notoriented in the reverse direction, which would render the belt conveyor74 ineffective for the scooping and transport of toner.

Next, a fourth embodiment will be described. The fourth embodiment issimilar to the third embodiment, except for the stationary shaft of theidle gear 94.

Referring to FIG. 21, the stationary shaft 128 of the idle gear is madeof the same material as the side frame or toner recycling transportingportion 70, and forms one part of the side frame or toner recyclingtransporting portion 70. The idle gear 94 itself may also be made of thesame material.

The stationary shaft 128 fits into a central hole of the idle gear 94,as indicated by the dotted line in FIG. 22, permitting the idle gear 94to turn freely, as indicated by arrow J. The sides of the stationaryshaft 128 have a plurality of wedge-shaped grooves 132 (two grooves inthe drawing), which are comparatively wide at the end 134 not attachedto the side frame or toner recycling transporting portion 70, and arenarrower at the attached end.

During printing, grains of toner or other foreign matter may find theirway into the space between the idle gear 94 and its stationary shaft128. The rotary motion of the idle gear 94 in direction J rolls thesegrains of foreign matter around the stationary shaft 128 in thedirection of arrow K in FIG. 22, so that in a short time they drop intothe grooves 132 in the shaft 128. As foreign matter collects in thesegrooves 132, the rotation of the idle gear 94 forces the foreign matteragainst the slanted side faces 136 of the grooves, thereby causing theforeign matter to slide in the direction of arrow L toward the free end134 of the shaft 128. Foreign matter reaching the end 134 of a groove132 can drop out into, for example, a passage provided in the side frameor toner recycling transporting portion 70, which will be described in alater embodiment.

By providing an escape route for foreign matter caught between the idlegear 94 and its stationary shaft 128, the grooves 132 prevent foreignmatter from accumulating and causing friction between the idle gear 94and shaft 128. The torque load on the motor that drives thephotosensitive drum 24 and the toner recycling transporting mechanism isaccordingly not increased due to such friction, and printingirregularities that might be caused by such friction are avoided.

Next, a fifth embodiment will be described. The fifth embodiment issimilar to the fourth embodiment, except for the groove pattern on thestationary shaft 128 of the idle gear 94.

Referring to FIG. 23, in the fifth embodiment, the stationary shaft 128in the fifth embodiment has a groove 138 that follows a counterclockwisehelical path toward the end 140 of the shaft that is not attached to theside frame 70. This helical groove 138 serves the same purpose as thegrooves in the fourth embodiment. If particles of toner or other foreignmatter enter the space between the idle gear 94 and stationary shaft128, they are carried in the direction of arrow K by the rotation of theidle gear 94 until they drop into the helical groove 138. Contact withthe rear side wall 142 of the helical groove 138 then pushes the foreignmatter toward the free end 140 of the shaft, to be discharged into anappropriate passage.

The effect of the fifth embodiment is similar to the effect of thefourth embodiment: friction between the idle gear 94 and its stationaryshaft 128 is avoided, a steady torque load is maintained on the drivingmotor, and printing irregularities are prevented.

Next, a sixth embodiment will be described. The sixth embodiment issimilar to the fifth embodiment, but locates the helical groove on theinner surface of the idle gear 94 instead of the outer surface of itsshaft.

Referring to FIG. 24, the idle gear 94 in the sixth embodiment has ahelical groove 144 that follows a clockwise helical path around theinner surface 146 of the idle gear 94, from the end of the idle gear 94adjacent the side frame 70 to the opposite end 148. The outer surface ofthe stationary shaft 128 is smooth. If particles of foreign matter enterthe space between the idle gear 94 and shaft 128, they are carried intothe helical groove 144, then carried toward the end 148 of the idle gear94 by contact with the rear side wall 150 of the helical groove 144, andthus discharged into an appropriate passage.

The sixth embodiment has the same effects as the fourth and fifthembodiments in reducing friction between the idle gear 94 and the shaft128, maintaining a steady torque load on the driving motor, andpreventing printing irregularities.

Next, a seventh embodiment will be described. The seventh embodimentprovides for the return of toner from the belt driving gear 92 to thebelt conveyor 74. The seventh embodiment also provides a passage fortoner discharged from between the idler gear 94 and its stationary shaftin the fourth, fifth, and sixth embodiments.

Referring to FIG. 25, this passage 152 starts below the belt drivinggear 92, extends generally parallel to the channel 72 for a distance,then joins the channel 72 at a point from which the channel 72 slopesdownward toward the toner collection chamber 66.

As described in the preceding embodiment, the belt conveyor 74 scoops uptoner from the toner collection chamber 66 at the pick-up station 78,carries the toner to the discharging station 80, and discharges thetoner into the toner delivery chamber 82. Some of the toner, however,adheres to the belt conveyor 74 and fails to be discharged. Some of thisadhering toner is picked up by the teeth of the belt driving gear 92when they engage the teeth of the belt conveyor 74, and adheres to theteeth of the belt driving gear 92. This adhering toner then falls fromthe belt driving gear 92 into the passage 152, is returned to thechannel 72, is picked up again by the belt conveyor 74, and is carriedinto the toner collection chamber 66.

The passage 152 in the seventh embodiment prevents toner fromaccumulating in the space around the belt driving gear 92, where suchtoner might clog the teeth of the belt driving gear 92 and generallyinterfere with the rotation of this gear 92. By preventing suchaccumulation of toner, the seventh embodiment contributes to themaintenance of a steady torque load on the driving motor and theprevention of printing irregularities.

Next, an eighth embodiment of the invention will be described.

Referring to FIG. 26, in place of the pulley 76 and screw conveyor 84 ofthe first embodiment, the eighth embodiment has a toothed screw conveyor154 extending into the toner delivery chamber 82 in substantially thesame position as the screw conveyor 84 of the first embodiment. Thetoothed screw conveyor 154 comprises a shaft 156 and a helical screw158, with teeth 160 extending from the outer edges of the helical screw158 at one end. These teeth 160 engage lateral ribs 162 on the beltconveyor 74.

FIG. 27 shows a perspective view of the toothed screw conveyor 154. Theteeth 160 are disposed at the end of the helical screw 158, where thehelical screw 158 meets the belt conveyor 74.

During printing, the shaft 156 of the toothed screw conveyor 154 isdriven in the direction of arrow M in FIG. 26 by a gear train not shownin the drawing. The teeth 160 mesh with the lateral ribs 162 and thebelt conveyor 74 is driven in the direction of arrow B, carrying tonerfrom the toner collection chamber 66 to the toner delivery chamber 82.The helical screw 158 then carries the toner to the appropriate positionin the toner delivery chamber 82 for delivery to the developing unit 28.

By replacing the pulley 76 and screw conveyor 84 of the first embodimentwith a single toothed screw conveyor 154, the eighth embodiment reducesnumber of parts and hence the cost of the printing process cartridge 58.The cartridge 58 also becomes easier and thus less expensive toassemble.

Next, a ninth embodiment will be described. Referring to FIG. 28, theninth embodiment has the same configuration as the first embodiment, butwith an additional projection 164 on the outer wall of the channel 72just above the discharging station 80. This projection 164 interferesslightly with the belt conveyor 74, by brushing against the lateral ribsof the belt conveyor 74, for example, thereby causing vibrations thatloosen toner from the belt conveyor 74, so that the toner does notadhere to the belt conveyor 74 but falls into the toner delivery chamber82. By reducing the amount of toner that fails to be released at thedischarging station 80, the ninth embodiment enables the toner recyclingtransporting mechanism to operate more efficiently.

Next, a tenth embodiment will be described. Referring to FIG. 29, thetenth embodiment has the same configuration as the first embodiment, butwith the addition of a flexible-blade 166 that extends into the channel72 just above the discharging station 80. This flexible blade 166 servesthe same purpose as the projection in the ninth embodiment, slightlyinterfering with the belt conveyor 74 and thereby causing vibrationsthat loosen toner from the belt conveyor 74, so that more of the tonerfalls into the toner delivery chamber 82 and less toner adheres to thebelt conveyor 74.

The preceding embodiments can be combined in various ways not explicitlymentioned above. For example, the projection 164 of the ninth embodimentor the flexible blade 166 of the tenth embodiment, can be combined withany of the preceding embodiments.

All of the embodiments described above have the advantages mentioned inthe first embodiment. The width of the printing process cartridge 58 isreduced because the belt conveyor 74 is disposed in a channel 72 thatloops around the ends of the shafts of existing rollers in the printingprocess cartridge 58, without extending beyond the ends of these shafts.No worm gear is required, so the load on the driving motor is reduced,and motion irregularities are avoided. In addition, the number of partsin the toner recycling transporting mechanism is reduced, so the cost ofthe printing process cartridge 58 is reduced, including both thematerials cost and the cost of assembly.

Those skilled in the art will recognize that other embodiments arepossible within the scope claimed below.

1. A method of recycling transporting toner in an electrophotographicprinter having a photosensitive drum on which a latent image is formed,a developing unit for developing the latent image by application oftoner, and a transfer unit for transferring the developed image from thephotosensitive drum to a printing medium, comprising the steps of:removing toner from said photosensitive drum after transfer of saidimage to said printing medium; collecting the toner thus removed in atoner collection chamber; using a belt conveyor to transport the tonerfrom said toner collection chamber to a toner delivery chamber;returning the toner from said toner delivery chamber to said developingunit; using an idle rotatable element turning on a shaft to move saidbelt conveyor, said rotatable element rotating in relation to saidshaft; and allowing foreign matter that becomes caught between said idlerotatable element and said shaft to escape through a groove formed inone of an outer surface of said shaft and an inner surface of said idlerotatable element.
 2. A method of recycling transporting toner in anelectrophotographic printer having a photosensitive drum on which alatent image is formed, a developing unit for developing the latentimage by application of toner, and a transfer unit for transferring thedeveloped image from the photosensitive drum to a printing medium,comprising the steps of: removing toner from said photosensitive drumafter transfer of said image to said printing medium; collecting thetoner thus removed in a toner collection chamber; using a belt conveyorto transport the toner from said toner collection chamber to a tonerdelivery chamber; returning the toner from said toner delivery chamberto said developing unit; driving said belt conveyor by rotating atoothed wheel engaging said belt conveyor; and allowing toner that ispicked up by said toothed wheel from said belt conveyor to drop througha passage and return to said belt conveyor.
 3. A method of recyclingtransporting toner in an electrophotographic printer having aphotosensitive drum on which a latent image is formed, a developing unitfor developing the latent image by application of toner, and a transferunit for transferring the developed image from the photosensitive drumto a printing medium, comprising the steps of: removing toner from saidphotosensitive drum after transfer to said image to said printingmedium; collecting the toner thus removed in a toner collection chamber;using a belt conveyor to transport the toner from said toner collectionchamber to a toner delivery chamber; returning the toner from said tonerdelivery chamber to said developing unit; and driving a screw conveyorhaving a toothed end, said screw conveyor conveying said toner from oneend of said toner delivery chamber toward a more central part of saidtoner delivery chamber, the toothed end of said screw conveyorsimultaneously driving said belt conveyor.
 4. A toner recyclingtransporting mechanism for an electrophotographic printer having aphotosensitive drum on which a latent image is formed, a developing unitfor developing said latent image by application of toner, and a transferunit for transferring the developed image to a printing medium,comprising: a toner recycling transporting portion, having a channelforming a loop, with a pick-up station at a first position in said loopand a discharging station at a second position in said loop; a cleaningunit attached to said toner recycling transporting portion, for removingsaid toner from said photosensitive drum after transfer of said image tosaid printing medium, said cleaning unit having a toner collectionchamber opening into said channel at said pick-up station for holdingthe toner thus removed, and a first conveyor for conveying the toner insaid toner collection chamber to said pick-up station; a toner deliverychamber attached to said toner recycling transporting portion, openinginto said chamber at said discharging station; and a second conveyor inthe form of a belt conveyor disposed in and guided by said channel, forconveying said toner from said pick-up station to said dischargingstation.
 5. The toner recycling transporting mechanism of claim 4,wherein said photosensitive drum, said developing unit, and said tonerrecycling transporting portion form part of a changeable cartridge insaid electrophotographic printer.
 6. The toner recycling transportingmechanism of claim 4, further comprising a pulley disposed inside saidloop, in contact with said belt conveyor for driving said belt conveyor.7. The toner recycling transporting mechanism of claim 4, furthercomprising a toothed wheel disposed outside said loop, in contact withsaid belt conveyor, for driving said belt conveyor.
 8. The tonerrecycling transporting mechanism of claim 7, wherein said tonerrecycling transporting portion has a passage disposed below said toothedwheel and communicating with said channel, for receiving toner that ispicked up by said toothed wheel from said belt conveyor and thendropped, and returning said toner to said belt conveyor.
 9. The tonerrecycling transporting mechanism of claim 4, wherein said secondconveyor is further comprising a third conveyor which is in the form ofa screw conveyor with teeth at one end, said teeth engaging and drivingsaid belt second conveyor.
 10. The toner recycling transportingmechanism of claim 4, wherein said belt conveyor has an outer surfacewith lateral ribs for carrying said toner.
 11. The toner recyclingtransporting mechanism of claim 4, wherein said belt conveyor has anouter surface with depressed pockets for carrying said toner.
 12. Thetoner recycling transporting mechanism of claim 4, wherein said beltconveyor has cut-out holes for carrying said toner.
 13. The tonerrecycling transporting mechanism of claim 4, wherein said belt conveyorhas an outer surface with teeth for carrying said toner.
 14. The tonerrecycling transporting mechanism of claim 13, wherein said teeth are setat an angle toward a direction of travel of said belt conveyor.
 15. Thetoner recycling transporting mechanism of claim 4, wherein said beltconveyor has a longitudinal rib, and said channel has a grooveaccommodating said longitudinal rib, thereby preventing said beltconveyor from being installed in an incorrect orientation in saidchannel.
 16. The toner recycling transporting mechanism of claim 4,further comprising: a shaft attached to said toner recyclingtransporting portion, having a grooved cylindrical surface; and an idlerotatable element mounted on said shaft, for moving said belt conveyor,said rotatable element rotating in relation to said shaft; the groovedcylindrical surface of said shaft providing an escape route for foreignmatter that becomes caught between said shaft and said idle rotatableelement.
 17. The toner recycling transporting mechanism of claim 16,wherein the grooved cylindrical surface of said shaft has at least onelongitudinal wedge-shaped groove.
 18. The toner recycling transportingmechanism of claim 16, wherein the grooved cylindrical surface of saidshaft has a helical groove.
 19. The toner recycling transportingmechanism of claim 16, wherein said idle rotatable element is an idlegear transmitting torque to said belt conveyor.
 20. The toner recyclingtransporting mechanism of claim 4, further comprising: a shaft attachedto said toner recycling transporting portion; and an idle rotatableelement mounted on said shaft, for moving said belt conveyor, saidrotatable element rotating in relation to said shaft, said idlerotatable element having a grooved inner surface in contact with saidshaft, the grooved inner surface of said idle rotatable elementproviding an escape route for foreign matter that becomes caught betweensaid shaft and said idle rotatable element.
 21. The toner recyclingtransporting mechanism of claim 20, wherein the grooved inner surface ofsaid idle rotatable element has a helical groove.
 22. The tonerrecycling transporting mechanism of claim 21, wherein said idlerotatable element is an idle gear transmitting torque to said beltconveyor.
 23. The toner recycling transporting mechanism of claim 20,wherein said idle rotatable element is an idle gear transmitting torqueto said belt conveyor.
 24. The toner recycling transporting mechanism ofclaim 4, further comprising an interfering member making contact withsaid belt conveyor at said discharging station, thereby loosening saidtoner from said belt conveyor.
 25. The toner recycling transportingmechanism of claim 24, wherein said interfering member comprises aprojection in an outer wall of said channel.
 26. The toner recyclingtransporting mechanism of claim 24, wherein said interfering membercomprises a flexible blade attached to said toner recycling transportingportion and extending into said channel.
 27. The toner recyclingtransporting mechanism of claim 4, wherein: said developing unit has aroller turning on a shaft; and said toner recycling transporting portionforms a side frame supporting one end of said shaft.
 28. The tonerrecycling transporting mechanism of claim 27, wherein said channel formsa loop around said one end of said shaft.
 29. The toner transportingmechanism of claim 4, wherein said toner transporting portion forms aside frame supporting one end of a shaft of said photosensitive drum.30. The toner transporting mechanism of claim 29, wherein said channelforms a loop around said one end of said shaft.
 31. A method oftransporting toner in an electrophotographic printer having aphotosensitive drum on which a latent image is formed, a developing unitfor developing the latent image by application of toner, and a transferunit for transferring the developed image from the photosensitive drumto a printing medium, comprising the steps of: removing toner from saidphotosensitive drum after transfer of said image to said printingmedium; collecting the toner thus removed in a toner collection chamber;and slidably guiding a belt conveyor along a channel connecting the tonecollection chamber to a toner delivery chamber to transport toner fromthe toner collection chamber to the toner delivery chamber.
 32. A tonertransporting mechanism for an electrophotographic printer having aphotosensitive drum on which a latent image is formed, a developing unitfor developing said latent image by application of toner, and a transferunit for transferring the developed image to a printing medium,comprising: a toner transporting portion, having a channel with apick-up station at a first position along said channel and a dischargestation at a second position along said channel; a cleaning unitattached to said toner transporting portion for removing said toner fromsaid photosensitive drum after transfer of said image to said printingmedium, a toner collection chamber opening into said channel at saidpick-up station for holding the toner thus removed, and a first conveyorfor conveying the toner in said toner collection chamber to said pick-upstation; a toner delivery chamber attached to said toner transportingportion, opening into said channel at said discharging station; and asecond conveyor in the form of a belt conveyor disposed in and slidablyguided by said channel, for conveying said toner from said pick-upstation to said discharging station.
 33. The toner transportingmechanism of claim 32, wherein said photosensitive drum, said developingunit, and said toner transporting portion form part of a changeablecartridge in said electrophotographic printer.
 34. The tonertransporting mechanism of claim 32, further comprising a third conveyorwhich is in the form of a screw conveyor with teeth at one end, saidteeth engaging and driving said second conveyor.
 35. The tonertransporting mechanism of claim 32, wherein said developing unit has aroller turning on a shaft; and said toner transporting portion forms aside frame supporting one end of said shaft.
 36. The toner transportingmechanism of claim 32, wherein said toner transporting portion forms aside frame supporting one end of a shaft of said photosensitive drum.37. The toner transporting mechanism of claim 32, wherein said secondconveyor has a surface with lateral ribs for carrying said toner. 38.The toner transporting mechanism of claim 32, wherein said secondconveyor has a surface with depressed pockets for carrying said toner.39. The toner transporting mechanism of claim 32, wherein said secondconveyor has cut-out holes for carrying said toner.
 40. The tonertransporting mechanism of claim 32, wherein said second conveyor has asurface with teeth for carrying said toner.
 41. The toner transportingmechanism of claim 40, wherein said teeth are set at an angle toward adirection of travel of said second conveyor.
 42. The toner transportingmechanism of claim 32, wherein said channel is formed in a side frame.